摘要:

Structure classes and changes in the vegetation attributable to the altitude of the terrain were studied in the Hammastunturi virgin coniferous forest area. The area is located in Finnish Lapland, approximately 250–350 km to the north of the Arctic Circle (68°15'N; 68°45'N). The following forest classes were formed on the basis of the ground vegetation and stand coverage: (1) Pine stands, with birch admixture (n=14), (2) Vaccinium‐vitis‐idaea‐type pine stands (n= 24), (3) Vaccinium myrtillus‐type pine stands (n =17), (4) mixed stands, dominated by pine (n= 8), (5) mixed stands, dominated by spruce (n=18), (6) paludified spruce stands (n= 3) and (7) vigorously growing spruce stands (n= 6). The forest structure classes were depicted using DCA ordinates. The differences were more distinct than those between the normal forest type classifications of the same sample plots. The basal area and volume of pine decreased with increasing altitude, while the proportion of spruce on those sample plots where it was present increased. Birch was present at an equal frequency at all altitudes. The floral composition and between‐species abundance changed along with increasing altitude. The change in floral frequencies could not be designated to a specific altitude zone.

ISSN:0282-7581    

DOI:10.1080/02827589809383005

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Structural changes were analysed in two virgin forest stands by comparing tree data collected in 1922 and 1994. One stand was dominated by pine(Pinus sylvestrisL.), while the other was a mixed pine and spruce(Picea abies(L.) Karst.) stand. Between 1922 and 1994, the standing volume of living trees increased by 46% in the pine stand and by 71% in the mixed stand, while the volume of dead trees increased by 126% and 87%, respectively. The proportion of spruce increased at the expense of pine and deciduous tree species in both stands. The density of conifer seedlings fell by 90% between the two dates, and diameter distributions changed considerably as a result of changed regeneration conditions and differing mortality rates of different size classes. The data suggest that a reversed J‐shaped diameter distribution of spruce could be a temporary phenomenon rather than a stable long‐term characteristic. The structural changes found, which seem to be characteristic of many protected forests, appear to be due to the absence of fire disturbance. It is questionable, therefore, that the policy of fire prevention is consistent with the major aims of nature conservation programmes.

ISSN:0282-7581    

DOI:10.1080/02827589809383006

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dendrochronological dating of fire scars was used to determine the history of forest fires, and the effects of the fires and of slash‐and‐burn cultivation on forest structure were studied in eastern Finland. A total of 67 fire years were dated over an area of 26 km2. Forest fires increased towards the end of the 17th century and again towards the end of the 18th century, but decreased markedly in the middle of the 19th century. The mean fire interval was shorter near the historically known slash‐and‐burn cultivation areas than elsewhere. A forest survey map from 1913 was used to reconstruct the forest structure after the cessation of slash‐and‐burn cultivation and forest fires. This map showed that most of the younger forests were situated near old slash‐and‐burn cultivation areas, while the older forests were situated farther away from these. The proportion of deciduous trees decreased with increasing distance from slash‐and‐burn cultivation areas.

ISSN:0282-7581    

DOI:10.1080/02827589809383007

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The variation in timber prices is one of the main sources of uncertainty in forest planning. Timber prices in Finland are modelled in this study for the purposes of forest planning calculations. The model constructed consists of two different processes, one for price peaks, and the other for the rest of the time series. Modelling of price peaks, i.e. the exceptionally high timber prices in the early 1950s and mid‐1970s, is important especially when studying the adaptive behaviour of forestry decision‐makers. The AR(1) model is used in modelling the rest of the time series. The model can be used to simulate realistic future timber price scenarios, thus enabling the study of uncertainty in forest planning caused by timber prices. Although timber prices in Finland are used, similar methods could be applied in many other countries, too. The modelling approach presented could also be applied in simulating the prices of other raw materials, e.g. oil and some metals.

ISSN:0282-7581    

DOI:10.1080/02827589809383008

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Assessment of the visual impacts of land‐use changes is often neglected in the planning of agriculture and forestry. This study presents an approach for management planning, when landscape value is a parallel goal with numerical variables such as income. In this study, planning is based on the goals of both landowners and other interested groups. The importance of different goals and the utility of alternative plans are evaluated using the analytic hierarchy process (AHP). Two‐stage planning is used to produce separate management alternatives for each farm at the first stage and further for the whole planning area. The first stage guarantees the feasibility of alternative plans at the farm level and the second combines alternatives in an acceptable way at the areal level. The near‐view scene is assessed from numerical values and the distant‐view scene from graphical visualizations. The feasibility of the planning approach is illustrated with a case study. In the future, more work is needed to develop indices for describing landscape numerically based on human preferences.

ISSN:0282-7581    

DOI:10.1080/02827589809383009

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study presents an econometric analysis of the spatial integration of the Nordic timber market as reflected in timber prices. The statistical model is a vector autoregressive (VAR) model with cointegration. The degree of spatial integration is tested through a cointegration analysis and a complete identification of the statistical model's long‐run structure. When the results were interpreted in terms of factor price equalization and efficient commodity arbitrages, the Nordic markets were found to be strongly integrated. The pattern of interdependence is investigated through an analysis of the model's short‐run structure and interpreted in terms of Granger causality. Finland, and to some extent Sweden, were found to act as “price‐leaders” in the long run and Denmark and Norway were very sensitive to changes in timber prices in competing countries.

ISSN:0282-7581    

DOI:10.1080/02827589809383010

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The objective of the present study was to determine the accuracy of digitized colour‐infrared aerial photographs for predicting forest habitats defined by dominant tree species, stand age and ground vegetation in order to assess the structural diversity of forests. The solar direction and viewing angle at exposure time exert strong effects on illumination by causing a bidirectional reflectance effect. As a result, the same forest habitat will have totally different reflectance values, depending on its position in the photograph. Digital tone values were thus calibrated prior to the stratification, using empirical regression‐calibration or rationing methods. Linear regression calibration to the principal‐point level of the photographs, in which the mean pixel value was modelled as a function of sun and sensor position at the time of exposure, was shown to be the most effective method. The results showed that regression calibration significantly improved stratification accuracies. Separation of 12 habitat types was accomplished with 85.3% accuracy and 48 habitat types with 57.7% accuracy. The results also indicated that final stratification accuracy is very dependent on the prestratification needed, since the bidirectional reflectance effect in aerial photographs differs in various habitat types.

ISSN:0282-7581    

DOI:10.1080/02827589809383011

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Simple diameter at breast height (dbh) distribution and dimensional measures are nowadays insufficient to describe the composition of forest stands for sawing production planning. Marked price differences between different lumber grades means that sawmills also need reliable information about the qualitative composition of stands. Procedures for creating bivariate dbh/dead‐branch height distributions using the multivariate kernel method and generating lists of surrogate trees for sawing production planning are offered here. The test results indicate that the multivariate kernel method is superior to calculating smoothing of dbh and dead‐branch height separately.

ISSN:0282-7581    

DOI:10.1080/02827589809383012

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0282-7581    

DOI:10.1080/02827589809383013

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0282-7581    

DOI:10.1080/02827589809383014

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor